نوع مقاله : مقاله پژوهشی
نویسندگان
1 گروه مهندسی آب- دانشکده علوم کشاورزی- دانشگاه گیلان- رشت- ایران
2 هیات علمی /گروه مهندسی آب- دانشکده علوم کشاورزی- دانشگاه گیلان- رشت- ایران
چکیده
کلیدواژهها
موضوعات
عنوان مقاله [English]
نویسندگان [English]
This research was carried out to determine the simultaneous optimal management of nitrogen (N) fertilizer and the time and duration of mid-season drainage (MSD) of rice from an environmental point of view. This experiment was conducted in three treatments: application of N fertilizer and then drainage 7 days later for 7 days (T1), drainage for 7 days and then application of N fertilizer (T2), and drainage for 10 days and then application of N fertilizer (T3). The control treatment included fertilization at the same time as T1 treatment and without mid-season drainage.The quality parameters of drain water were measured. The results indicated that the time of applying fertilizer and drainage has a direct effect on pH. The average EC during the growth period in T2 and T3 decreased by 46 and 73%, respectively, compared to T1. The trend of NH4+ changes was upward before MSD, but after MSD, it decreased by 23% in T1 and 54% on average in T2 and T3. The average concentration of NO3- in the end season in T1, T2, and T3 was 22, 36, and 69% lower, respectively, and PO43- was 29, 31, and 67% lower than in MSD. The statistical analysis showed that the effect of time and treatments on SAR, and Cl- was insignificant. Applying fertilizer after drainage for 10 days has lower negative impact on environment. Compating yield and component yield in treatments show that T2 (7 days mid drainage and then appling nitrogen fertilizer) is a more appropriate option.
کلیدواژهها [English]
The effect of simultaneous management of nitrogen fertilizer and subsurface drainage of rice cultivation on drainage water quality
EXTENDED ABSTRACT
One of the most important food products of Iran is rice. One strategy for water management during the rice growing season is mid-season drainage, which may be facilitated by subsurface drainage. Also, at the time of harvest, the water in the soil profile should be drained and subsurface drainage has a better performance than surface drainage in this regard. Mid-season and end-season drainage provides conditions for crop growth and affecting the qualitative and quantitative performance of rice and the possibility of mechanized harvesting, and as a result, removing toxic substances, provides the development of rice cultivation. The use of nitrogen fertilizer is one of the most important factors in rice production and plays a key role in its performance. Excessive nitrogen application poses a high risk of nitrate leaching below the root zone and environmental consequences, so nitrogen fertilizer management is important. Therefore, the aim of this research is the mutual effect of drainage and fertilization in the mid-season drainage of rice cultivation and its effect on drainage water.
To determine the simultaneous optimal management of nitrogen fertilizer and the time and duration of Mid and end season drainage, a study was conducted at the Faculty of Agriculture of Gilan University located in Rasht city. 9 lysimeters with a diameter and height of 25 and 50 cm, respectively, made of PVC were used for rice cultivation and experiments. To control the drain outlet, a valve was installed at the outlet of the lysimeter, and the lysimeters were aligned in an open but sheltered space to prevent the effect of possible rain on the drainage process. The lysimeters were filled with the soil of paddy fields with loamy texture. This experiment was conducted in three treatments: 1- application of N fertilizer and then drainage 7 days later for 7 days (T1), 2- drainage for 7 days and then application of N fertilizer (T2) and 3- drainage for 10 days and then application of N fertilizer (T3) was done. Mid and end season drainage were carried out at the tillering stage and crop harvesting, respectively, and other times, flood irrigation method to a depth of 5cm was implemented. The parameters of drainage water including acidity (pH), electrical conductivity (EC), total suspended solids (TSS), sodium adsorption ratio (SAR) and the concentration of nitrate (NO3-), nitrite (NO2-), ammonium (NH4+), phosphate (PO43-), sulfate (SO42-) and chloride (Cl-) were measured. Finally, the results obtained from the study were statistically analyzed using SAS software and repeated measure experimental design.
The comparison of pH before mid and end season drainage showed that T2 had a different behavior than T1 and T3. The average electrical conductivity during the growth period in T2 and T3 decreased by 46 and 73%, respectively, compared to T1. The trend of ammonium changes was upward before MSD, but after MSD, it decreased by 23% in T1 and 54% on average in T2 and T3. The average concentration of nitrate in end season in T1, T2, and T3 was 22, 36, and 69% lower, respectively, and phosphate was 29, 31, and 67% lower than in MSD. The results of statistical analysis showed that the effect of time and treatments on SAR and Cl- was not significant. From the environmental pointof view, applying fertilizer after drainage for 10 days is a more appropriate option than the other two treatments. Stetstical analysis on yield and component yield show, T2 is better option.
The results showed that T3 treatment led to a decrease in electrical conductivity, total suspended solids, concentration of ammonium, nitrite, nitrate, phosphate and chloride in the drain water and a decrease in negative environmental consequences. According to the results of this research, mid-season drainage for 10 days and then nitrogen fertilization is recommended. Also, T2 product more yield than other tretments. The final decision to choose a better option also depends on the amount of water used to saturate the soil after drainage and yield. Therefore, more studies should be done on the continuity of drainage and its effect on the quality of drainage water and the productivity of irrigation water.
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